Note: Descriptions are shown in the official language in which they were submitted.
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REINFORCING MEMBER HAVING A PROJECTION ON ITS SURFACE
The present invention relates to a reinforcing member
made of a synthetlc resin which is provided with at least
one projection on the circumferential surface.
For the purpose of stabilizing rock in a tunnel,
there has been known a technique that holes are formed in
the rock and reinforcing members referred to as lock
bolts made of steel are embedded in the rock. However,
since the steel lock bolts are apt to cause corrosion
under high temperature and high humidity condition in the
tunnel thereby inviting reduction in strength and
rigidity of the lock bolts, attention is paid to a lock
bolt made of a synthetic resin which has corrosion
resistance and good processability.
Also, for the purpose of reinforcing a concrete
structure, attention is paid to a synthetic resin
reinforcing member as a substitute member for steel bar,
which is provided with at least one projection on its
circumferential surface to increase connection to the
rock or the concrete structure.
lt is common that reinforcing fibers having a high
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tensile strength such as carbon fibers are contained i.f'
the synthetic resin reinforcing member to obtain a
tensile strength same as or higher than the steel
reinforcing member.
As a method of forming a projection on the
circumferential surface of the fiber reinforced synthetic
resin reinforcing member, there has been known a method
of shaving the circumferential surface of the member
(referred to, for instance, Japanese Unexamined Patent
Publication ~o. 122655/1984). The shaving method has,
however, disadvantage such that long fibers for
reinforcement are cut when the reinforcing member is
shaved whereby reduction in tensile strength in the
longitudinal direction of the reinforcing member is
caused, and the projection formed by shaving is easily
broken.
The inventors of the present invention have got an
idea of forming the projection by wrapping continuous
fibers such as a glass roving on the circumferential
surface of the reinforcing member. In studying formation
of the projection, it has been found that a part of the
continuous fibers such as the glass roving should be
embedded in and closely contact with the circumferential
surface in order to form the projection providing good
adhesiveness to the circumferential surface. However, it
was difficult in the conventional technique to form the
projection having a sufficient height.
It is an object of the present invention to provide a
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reinforcing member in which at least one projection
havinq sufficient heightness is formed in close contact
with -the surface of the reinforcing member made of a
synthetic resin.
The foregoing and the other objects of the present
invention have been attainted by providing a reinforcing
member having at least one projection on its surface,
said projection being formed by wrapping a cord-like
material on the circumferential surface of a synthetic
resin core material, characterized in that the cord-like
material is a twisted cord formed by twisting continuous
fiber bundles at a pitch in the range of from 3 turns/10
cm to 15 turns/10 cm.
In drawings:
Figure 1 is a diagram showing an example of a method
of producing the reinforcing member according to the
present invention;
Figures 2a and 2b are respectively diagrams showing a
state that twisted cords or non-twlsted continuous fibers
are adhered to the surface of a core material; and
Figures 3a, 3b and 3c are respectively diagrams
showing how the twisted cord is wrapped around the core
material.
Preferred embodiments of the present invention will
be described with reference to drawings.
Figure 1 shows a typical method of preparing the
reinforcing member of the present invention.
Continuous fibers 1 for reinforcement, such as a mat,
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a roving and so on is introduced in a vessel containiny a
molten thermosetting resin or a thermoplastic resin to
impregnate the resin in the fibers. The resin-
impregnated fibers are fed to a squeezing device 4 to
adjust an amount of the resin to be impregnated. The
fibers are passed through a draw die 5 together with
continuous reinforcing fibers 3 without impregnation of
the resin, if necessary, whereby a core material having a
predetermined shape in cross-section is continuously
produced in a non-cured or a semi-cured state. In the
non-cured or the semi-cured state of the surface of the
core material, a twisted cord 6 which is formed by
twisting a plurality of continuous fiber bundles such as
glass rovings (hereinbelow referred to simply as a
twisted cord) is wrapped on the surface of the core
material so that at least one projection of the twisted
cord 6 is formed as shown in Figures 3a to 3c. Then, the
core material with the twisted cord are bonded together
in the room temperature or in an oven 7, followed by
pulling it in a pulling device 8 and cut it at a required
length. Thus, the reinforcing member made of a synthetic
resin is produced.
In order to wrap the twisted cord 6 around the core
material 12 as shown in Figures 3a and 3b, the pulling
device 8 is stopped until each wrapping operation for the
twisted cord 6 is finished. Especially, in Figure 3a,
the twisted cord 6 is cut for each single turn of the
twisted cord 6. In Figure 3b, a plurality of turns of
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-the twisted cord 6 is connected by the same single
twisted cord 6 in the longitudlnal direction of -the core
material without cutting the twisted cord 6. Figure 3c
shows the core material on which the twisted cord 6 is
wrapped in a spira.l form. The spiral projection is
formed by warpping the twisted cord 6 while the core
material is continuously pulled.
Figures 2a and 2b respectively show a state of a
twisted cord 10 attached to the circumferential surface
of a core material 12 and a state a convéntional glass
rovings 11 are attached to the circumferential surface of
the core material 12. The twisted cord 10 is formed by
twisting two glass rovings having the same weight per
unit length. The glass rovings 11 consist of two
parallel glass rovings. In comparing the thickness tl of
the t.wisted cord lC with the thickness t2 of the glass
rovings in parallel arrangement, there is a relation of
t1 > t2 and therefore, there is a relation rl > r2.
Namely, the twisted cord 10 does not tend to sink in the
surface of the core material 12. Further, raised
portions 13 in the twisted cord 10 can be firmly
connected to the core material and a force of adhesion
increases in comparison with the glass rovings 11. having
a uniform press-contacting force. Accordingly, the
projection formed by the twisted cord provides good
adhesiveness to the core material and fairly high
projection can be realized.
The twisted cord may be previously impregnated with a
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resin to be non-cured or a semi-cured state. If a resin
permeable to the twisted cord is coated in non-cured
state on the circumferential surface of the core
material, the twisted cord without impregnation of a
resin may be wrapped around the core material. In a case
that the twisted cord is wrapped around the core
material, it is preferable to apply a ten-tion to the
twisted cord to increase adhesiveness between the core
material and the twisted cord. The twisted cord may be
one previously twisted, or may be twisted while the cord
is wrapped around the core material. The number of
continuous fiber bundles to be twisted to form the
twisted cord depends on the outer diameter of the core
material and the thickness of the twisted cord. The
number of glass rovings is generally 2~10, preferably 2
to 4. It is desirable that the thickness of a continuous
fiber bundle is selected from the range from 4 g/m - 10
g/m where the core material is circular rod body and
having a diameter of 1 cm. The number of pitch for
twisting the twisted cord depends on the diameter of the
core material, the thickness of the twisted cord and the
number of continuous fiber bundles to be twisted. It is
desirable for the twisted cord to have a pitch of 3
turns/10 cm ~ 15 turns/10 cm, preferably, a pitch of 5
turns/lOcm - 10 turns/10 cm when the twisted cord is
twisted by using two continuous fiber bundles and the
thickness of each bundle is in the range of 2 g/m - 3
g/m.
As a bundle of continuous fibers which constitues ~he
twisted cord, a glass roving formed by gathering glass
fiber fila~ents or a tow formed by gathering carbon fiber
filaments is used as a typical bundle of fibers. The tow
consisting of carbon fibers is preferably used when
tensile strength is required. Carbon fibers may be of
acrylics or rayon series. A preferred shape of the core
material is cylindrical or an angular column. However~
it is possible to use ~he core material having a
plate-like form having a flat shape in closs-section. It
is preferable that long reinforcing fibers such as a
roving of glass filaments or a tow of carbon filaments
are arranged in the central portion of the core material
and, if necessary, reinforcing fibers in a continuous
strand mat form is arranged on the circumferential
portion of the core material. The core material may be
formed in such a manner that the central portion of the
core material is constituted by the conventional steel
reinforcing member and a fiber reinforced synthetic resin
is coated on the central part.
The reinforcing rnember of the present invention can
be used as a lock bolt, a substitute member for a steel
bar or various reinforcing members for a concrete
structure and so on. Specifically, the reinforcing
member of the present invention is applicable to
construction and maintenance for, for instance, a marine
structure such as the platform of an oil rig which
requires high durability, a chemical plant, a traffic
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faciLities such as a road, or a bridge which suffers sa]t
damadge by, for instance, a snow-melting agent. Further,
the reinforcing member of the present invention can be
used as a seat of a beam for a fusion reactor or a linear
motor car by utilizing nature of non-magnetization. The
reinforcing fibers constituting the core material or the
twisted cord of the present invention may be inorganic
fibers such as boron fi~ers, various metal fibers and so
on besides the carbon fibers or glass fibers; natural or
synthetic fibers such as hemp, vinylon, aramid,
polyamide, polyester and so on. The above-mentioned
materials may be used independently or in any
combination. The reinforcing fibers may be used as a
chopped strand mat, a continuous strand mat, a surfacing
mat, non-woven fabrics, cloth, bias cloth, a roving and
so on. They may also be used independently or any
combination. On the other hand, for the resin
constituting the reinforcing member, when the reinforcing
member is used for reinforcing a concrete structure, an
~ epoxy resin or an epoxyaclyrate resin is preferably used
since the resin has a resistance to alkali in the
concrete material. However, besides epoxy series resins,
a thermosetting resin such as an unsaturated polyester
resin, a phenol resin, and a thermoplastic resin such as
a polycarbona-te resin, polyvinyl chloride, a polypropylen
resin may be used. The reinforcing fibers are mixed in
the core material in the range of from 40 to 80 vol.%,
preferably, from 60 to 80 vol.% to maintain sufficient
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strength and rigidity of the core material. Further, it
is desirable that an amount of the resin impregnated in
the projection formed by the twisted cord wrapped on the
surcumferential surface oE the core material is 50 vol
or higher.
Preparation Example l
An unsaturated polyester resin is impregnated in 22
glass rovings each having a thickness of 4.45 g/m. The
resin-impregnated glass rovings were passed in a draw die
having a diameter of 8.2 mm to form a glass fiber
reinforced circular bar as a core material. A projection
in a spiral form having a pitch of lO mm was formed by
wrapping around the core material a twisted cord formed
by glass rovings impregnated with unsaturated polyes-ter
resin, while the core material in non-cured or a
semi-cured state was continuously pulled. Then, the core
material having the projection was passed through an oven
having a temperature of 80 C to cure the projection and
the core material in one piece. The twisted cord formed
by twisting two glass rovings (each having a thickness of
2.22 g/m) at a rate of 8 turns/lO cm was used. As a
result, a reinforcing member (I) in which a spiral
projection of 2 mm wide and 2 mm high was firmly attached
to a glass fiber reinforced circular bar of a diameter of
8 mm at a pitch of lO mm was obtained.
Preparation Example 2
The same operation as in the preparation I was
carried out except tnat a twisted cord is prepared by
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twisting two glass rovings at a pitch of 15 turns/10 cms
whereby a reinforcing member (II) in which a spiral
projection of 2 mm wide and 2.5 mm high was firmly
attached onto a glass fiber reinforced circular bar of a
diameter of 8 mm at a pitch of 10 mm was obtained.
Preparation Example 3
The same operation as in the preparation 1 was
carried out except that two glass rovings were warpped
without twisting, whereby a reinforcing member (III) in
which a spiral projection of 2.5 mm wide and 1 mm high
was firmly attached to a glass fiber reinforced circular
bar of a diameter of 8 mm at a pitch of 10 mm was
obtained.
Preparation Example 4
The same operation as in the preparation example 1
was carried out except that two glass rovings without
twisting were wrapped onto the core material so that the
height of the projection was 0 mm, whereby a reinforcing
member (IV) in which a spiral projection of 2.5 mm wide
and 0 mm high was firmly attached to the glass fiber
reinforced circular bar of a diameter of 8 mm at a pitch
of 10 mm was obtained.
Example
At the center of cubic concrete body having a side of
100 mm, the reinforcing members (I) and (II) were
respectively embedded and fixed so as to pass through the
cubic body. The cubic concrete body is fixed to a
tension tester. One end of the reinforcing members is
respectively inser-ted in an steel sleeve and a resin
material is poured in the steel sleeve followed by curing
the resin material. The ends of the reinforcing members
are pulled through the sIeeve to measure a strength of
adhesion between the concrete body and the reinforcing
members. The adhesion strength of the reinforcing member
(I) was 150 kg/cm2 and the adhesion strength of the
reinforcing member (II) was 135 kg/cm .
Comparative Example
Measurements were conducted in the same manner as in
the example as to the reinforcing members (III) and (IV).
The adhesion strength of the reinforcing member (III) was
120 kg/cm and the adhesion strength of the reinforcing
member (IV) was 100 kg/cm .
According to the present invention, a reinforcing
member having at least one projection on the surface of
the reinforcing member made of a Eiber reinforced
synthetic resin can be effectively obtained. The
projection has a strong connecting force to the core
material since the twisted cord is formed by twisting
bundles of continuous fibers at an optimum pitch.
Accordingly, the reinforcing member of the present
invention imparts excellent effect as a lock bolt or a
substitute member for a steel bar.
